Treatment with drugs able to reduce iodine efflux significantly increases the intracellular retention time in thyroid cancer cells stably transfected with sodium iodide symporter complementary deoxyribonucleic acid

CONTEXT

One of the major limits of gene therapy with sodium iodide symporter (NIS), which enables cells to be subjected to radioiodine therapy, is that NIS-transfected cells rapidly release the intracellular iodine.

METHODS

We transfected human anaplastic (FRO) and medullary (TT) thyroid cancer-derived cell lines that were unable to take up iodine with human NIS cDNA. The possibility of increasing the iodine retention time by treating the transfected clones with myricetin, lithium, 17-(allylamino)-17-demethoxygeldanamycin (17-AAG), and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) was explored.

RESULTS

We obtained 19 FRO and 16 TT clones stably transfected with NIS. Twelve of 19 FRO and nine of 16 TT clones expressed the full-length NIS mRNA; 11 of 12 FRO and four of nine TT clones were able to take up radioiodine and correctly expressed NIS protein on the plasma membrane. Kinetic analysis of iodide uptake in the two clones (FRO-19 and TT-2) with the highest uptaking activity revealed that the plateau was reached after 30 min by FRO-19 and after 60 min by TT-2. The t(1/2) of the iodide efflux was 9 min in FRO-19 and 20 min in TT-2. The treatment of the two cell lines with four different drugs revealed that DIDS and 17-AAG, but not myricetin and lithium, significantly increased the intracellular iodide retention time in FRO-19, but not in TT-2.

CONCLUSIONS

We showed that 17-AAG and DIDS prolong the retention time of (131)I in NIS-transfected thyroid tumoral cells, thus reinforcing the hope of using this approach for future clinical application, especially in patients with thyroid carcinoma who are no longer responsive to conventional therapy.

Correlation between B-RAFV600E mutation and clinico-pathologic parameters in papillary thyroid carcinoma: data from a multicentric Italian study and review of the literature

Recently, a somatic point mutation of the B-RAF gene (V600E) has been identified as the most common genetic event in papillary thyroid carcinoma (PTC), with a prevalence variable among different series. Since discordant data on the clinico-pathologic features of B-RAF mutated PTC are present in the literature, the aim of the present co-operative study was to establish the prevalence of this genetic alteration and to perform a genotype-phenotype correlation in a large cohort of patients with PTC. To this purpose, a series of 260 sporadic PTCs with different histological variants were included in the study. The mutational analysis of the B-RAF gene was performed either by RT-PCR followed by single-stranded conformational polymorphism or by PCR and direct sequencing. Statistical analyses were obtained by means of chi2/Fisher's exact test and t-test. Overall, a heterozygous T > A transversion at nucleotide 1799 (V600E) was found in 99 out of 260 PTCs (38%). According to the histological type of the tumor, the B-RAF (V600E) mutation was present in 48.3% of cases of classic PTCs (85 out of 176), in 17.6% (nine out of 51) of follicular variants of PTCs, in 21.7% (five out of 23) in other PTC variants and in none of the ten poorly differentiated tumors. B-RAF (V600E) was significantly associated with the classic variant of PTC (P = 0.0001) and with an older age at diagnosis (P = 0.01). No statistically significant correlation was found among the presence of B-RAF (V600E) and gender, tumor node metastasis (TNM), multicentricity of the tumor, stage at diagnosis and outcome. In conclusion, the present study reports the prevalence of B-RAF (V600E) (38%) in the largest series of sporadic PTCs, including 260 cases from three different Italian referring centers. This prevalence is similar to that calculated by pooling together all data previously reported, 39.6% (759 out of 1914 cases), thus indicating that the prevalence of this genetic event lies around 38-40%. Furthermore, B-RAF (V600E) was confirmed to be associated with the papillary growth pattern, but not with poorer differentiated PTC variants. A significant association of B-RAF mutation was also found with an older age at diagnosis, the mutation being very rare in childhood and adolescent PTCs. Finally, no correlation was found with a poorer prognosis and a worse outcome after a median follow-up of 72 months.

Interleukin-6 release from human abdominal adipose cells is regulated by thyroid-stimulating hormone: effect of adipocyte differentiation and anatomic depot

Adipose cells are extrathyroidal targets of thyroid-stimulating hormone (TSH). TSH stimulates interleukin-6 (IL-6) release from adipocytes. We examined TSH responsiveness as a function of stage of differentiation or adipose tissue depot in cultured adipose cells and determined the effect of TSH on extrathyroidal IL-6 production in vivo. Stromal preadipocytes, isolated from human abdominal subcutaneous or omental adipose tissue, and their differentiated counterparts were studied. IL-6 protein concentration in the medium was measured after TSH stimulation. Basal IL-6 release was greater for preadipocytes than differentiated adipocytes, whether derived from subcutaneous or omental fat depots. A depot-dependent effect (omental > subcutaneous) on basal IL-6 release was observed for preadipocytes (1.6-fold, P < 0.05); a similar trend for differentiated adipocytes was not significant (6.2-fold, P > 0.05). IL-6 responsiveness to TSH was observed upon differentiation, but only for subcutaneous adipocytes (1.9-fold over basal, P < 0.001). To determine if TSH could stimulate IL-6 release from extrathyroidal tissues in vivo, we measured serum IL-6 levels from five thyroidectomized patients who received recombinant human (rh) TSH and found that levels increased by threefold on days 3 and 4 (P < 0.05) after its administration. Our data demonstrate that stage of differentiation and fat depot origin affect basal and TSH-stimulated IL-6 release from adipose cells in culture. Furthermore, rhTSH elevates serum IL-6 response in thyroidectomized patients, indicating an extrathyroidal site of TSH action.

Iodine biokinetics and dosimetry in radioiodine therapy of thyroid cancer: procedures and results of a prospective international controlled study of ablation after rhTSH or hormone withdrawal

Technical aspects and results of the dosimetric assessments of postoperative radioiodine ablation in the framework of an international, prospective, controlled, randomized, comparative study of the effectiveness of ablation therapy with 3.7 GBq (131)I in differentiated thyroid cancer after stimulation with recombinant human TSH (rhTSH) or by thyroid hormone withdrawal (THW) are presented.

METHODS

Sixty-three patients were randomized after thyroidectomy to either the THW or the rhTSH group. Scintigraphic neck images were acquired starting 48 h after radioiodine administration to assess biokinetics in the thyroid remnant. The activity in blood samples was quantified and data from whole-body probe measurements and scintigraphic whole-body scans were combined to deduce retention curves in blood and whole body, respectively. The absorbed dose to the blood was calculated using a modified approach based on the formalism of the MIRD Committee of the Society of Nuclear Medicine.

RESULTS

The effective half-time in the remnant thyroid tissue was significantly longer after rhTSH than THW (67.6 +/- 48.8 vs. 48.0 +/- 52.6 h, respectively; P = 0.01), whereas the observed differences of the mean 48-h (131)I uptakes (0.5% +/- 0.7% vs. 0.9% +/- 1.0% after THW; P = 0.1) and residence times (0.9 +/- 1.3 vs. 1.4 +/- 1.5 h after THW; P = 0.1) between the rhTSH and THW groups were not statistically significant. The specific absorbed dose to the blood was significantly (P <0.0001) lower after administration of rhTSH (mean, 0.109 +/- 0.028 mGy/MBq; maximum, 0.18 mGy/MBq) than after THW (mean, 0.167 +/- 0.061 mGy/MBq; maximum, 0.35 mGy/MBq), indicating that higher activities of radioiodine might be safely administered after exogenous stimulation with rhTSH.

CONCLUSION

Indication of an influence of the residence time of radioiodine in the blood on the fractional uptake into thyroid remnant was found. A novel regimen is proposed in which therapeutic activities to be administered are determined from the individual specific blood dose.

A comparison of short-term changes in health-related quality of life in thyroid carcinoma patients undergoing diagnostic evaluation with recombinant human thyrotropin compared with thyroid hormone withdrawal

CONTEXT

Thyroid carcinoma requires lifelong monitoring with serum thyroglobulin, radioactive iodine whole body scanning, and other imaging modalities. Levothyroxine (L-T4) withdrawal for thyroglobulin measurement and whole body scanning increases these tests' sensitivities but causes hypothyroidism. Recombinant human TSH (rhTSH) enables testing without L-T4 withdrawal.

OBJECTIVE

Our objective was to examine the impact of short-term hypothyroidism on the health-related quality of life (HRQOL) of patients after rhTSH vs. L-T4 withdrawal.

DESIGN, SETTING, AND PATIENTS

In this multicenter study, the SF-36 Health Survey was administered to 228 patients at three time points: on L-T4, after rhTSH, and after L-T4 withdrawal.

INTERVENTIONS

INTERVENTIONS included administration of rhTSH on L-T4 and withdrawal from thyroid hormone.

MAIN OUTCOME MEASURES

Mean SF-36 scores were compared during the two interventions and with the U.S. general population and patients with heart failure, depression, and migraine headache.

RESULTS

Patients had SF-36 scores at or above the norm for the general U.S. population in six of eight domains at baseline on L-T4 and in seven of eight domains after rhTSH. Patients' scores declined significantly in all eight domains after L-T4 withdrawal when compared with the other two periods (P < 0.0001). Patients' HRQOL scores while on L-T4 and after rhTSH were at or above those for patients with heart failure, depression, and migraine in all eight domains. After L-T4 withdrawal, patients' HRQOL scores were significantly below congestive heart failure, depression, and migraine headache norms in six, three, and six of the eight domains, respectively.

CONCLUSIONS

Short-term hypothyroidism after L-T4 withdrawal is associated with a significant decline in quality of life that is abrogated by rhTSH use.

Radioiodine ablation of thyroid remnants after preparation with recombinant human thyrotropin in differentiated thyroid carcinoma: results of an international, randomized, controlled study

CONTEXT

After surgery for differentiated thyroid carcinoma, many patients are treated with radioiodine to ablate remnant thyroid tissue. This procedure has been performed with the patient in the hypothyroid state to promote endogenous TSH stimulation and is often associated with hypothyroid symptoms and impaired quality of life. OBJECTIVE AND INTERVENTION: This international, randomized, controlled, multicenter trial aimed to compare the efficacy and safety of recombinant human TSH (rhTSH) to prepare euthyroid patients on L-thyroxine therapy (euthyroid group) to ablate remnant thyroid tissue with 3.7 GBq (100 mCi) 131I, compared with that with conventional remnant ablation performed in the hypothyroid state (hypothyroid group). Quality of life was determined at the time of randomization and ablation. After the administration of the 131-I dose, the rate of radiation clearance from blood, thyroid remnant, and whole body was measured.

RESULTS

The predefined primary criterion for successful ablation was "no visible uptake in the thyroid bed, or if visible, fractional uptake less than 0.1%" on neck scans performed 8 months after therapy and was satisfied in 100% of patients in both groups. A secondary criterion for ablation, an rhTSH-stimulated serum thyroglobulin concentration less than 2 ng/ml, was fulfilled by 23 of 24 (96%) euthyroid patients and 18 of 21 (86%) hypothyroid patients (P = 0.2341). Quality of life was well preserved in the euthyroid group, compared with the hypothyroid group, as demonstrated by their lower pretreatment scores on the Billewicz scale for hypothyroid signs and symptoms, 27 +/- 7 vs. 18 +/- 4 (P < 0.0001) and their significantly higher Short Form-36 Health Assessment Scale scores in five of eight categories. Euthyroid patients had a statistically significant one third lower radiation dose to the blood, compared with patients in the hypothyroid group.

CONCLUSIONS

This study demonstrates comparable remnant ablation rates in patients prepared for 131I remnant ablation with 3.7 GBq by either administering rhTSH or withholding thyroid hormone. rhTSH-prepared patients maintained a higher quality of life and received less radiation exposure to the blood.

RET/PTC3 rearrangement and thyroid differentiation gene analysis in a struma ovarii fortuitously revealed by elevated serum thyroglobulin concentration

Struma ovarii (SO) is usually asymptomatic and only in a few cases it is associated with thyrotoxicosis. The presurgical diagnosis is very uncommon. In the majority of cases a pelvic mass is discovered at physical examination or by abdominal ultrasound. Only the hystopathologic examination is able to reveal the characteristic features of SO, with thyroid cells organized in follicles as the main tumoral tissue constituent. The histologic recognition of malignancy is not easy and usually requires an exhaustive sampling of the lesion to evaluate the extracapsular invasion. We report the case of a 59-year-old woman who came to our observation for the fortuitous finding of elevated serum thyroglobulin (Tg) levels (600-800 ng/mL). Because the thyroid function was normal and the ultrasound showed only a subcentrimetric nodule, the clinical suspicious of a SO was considered. Ultrasound examination of the abdomen showed a solid mass of 2 cm in the left ovary. A (131)I uptake was observed at scintiscan in the site of the solid mass. Three months after the resection of the left ovary serum Tg levels were markedly reduced (106 ng/mL), and its values continued to decrease down to 34 ng/mL at last control. The histology showed that the ovarian mass was mainly constituted of thyroid tissue (98%), with no malignant features. The molecular analysis of several thyroid differentiation gene mRNAs in the SO tissue showed an abundant expression of all genes but pendrin (PDS). A reduced PDS mRNA expression might explain the defective thyroxine (T(4)) production. Despite the absence of malignant features, the expression of RET/PTC3 rearrangement was found, raising the possibility of a potential malignant nature of the tumor. A cancer-free period of 3-4 years, as in our patient, is not long enough to definitively exclude a late onset metastatic disease but, unfortunately, the patient died of nonmedical reasons. In conclusion, we report a case of SO that, to our knowledge, is the first in which the clinical suspicion arose from the inappropriately elevated presurgical serum levels of Tg. A quite exhaustive molecular analysis of thyroid specific genes and oncogenes provided two interesting findings: the low PDS mRNA expression, which may explain the low hormonal production and the absence of thyrotoxicosis and the presence of a RET/PTC3 rearrangement, which prompts the possibility of a late malignant evolution.

Post-surgical use of radioiodine (131I) in patients with papillary and follicular thyroid cancer and the issue of remnant ablation: a consensus report

OBJECTIVE

To determine, based on published literature and expert clinical experience, current indications for the post-surgical administration of a large radioiodine activity in patients with differentiated thyroid cancer.

DESIGN AND METHODS

A literature review was performed and was then analyzed and discussed by a panel of experts from 13 European countries.

RESULTS

There is general agreement that patients with unifocal microcarcinomas = 1 cm in diameter and no node or distant metastases have a <2% recurrence rate after surgery alone, and that post-surgical radioiodine confers recurrence and cause-specific survival benefits in patients, strongly suspected of having persistent disease or known to have tumor in the neck or distant sites. In other patients, there is limited evidence that after complete thyroidectomy and adequate lymph node dissection performed by an expert surgeon, post-surgical radioiodine provides clear benefit. When there is any uncertainty about the completeness of surgery, evidence suggests that radioiodine can reduce recurrences and possibly mortality.

CONCLUSION

This survey confirms that post-surgical radioiodine should be used selectively. The modality is definitely indicated in patients with distant metastases, incomplete tumor resection, or complete tumor resection but high risk of recurrence and mortality. Probable indications include patients with tumors >1 cm and with suboptimal surgery (less than total thyroidectomy or no lymph node dissection), with age <16 years, or with unfavorable histology.

Cyclic Cushing's disease with paradoxical response to dexamethasone

Cyclic Cushing's disease is an unusual disorder characterised by ACTH-dependent periodical increase of serum cortisol levels, clinically accompanied by peripheral edema, abnormalities of cardiac rhythm and hypokalemia. The condition may be unrecognised for years, since the typical features of Cushing's disease are usually absent due to the intermittent and brief duration of cortisol hypersecretion. We describe the case of a 42-yr-old man with Cyclic Cushing's disease due to an ACTH-producing pituitary macroadenoma, who presented two episodes of hypercortisolism in a 3-yr-period, clinically characterised by peripheral edema, hypokalemia and arrhythmia. The diagnosis was suspected because of a paradoxical increase of plasma ACTH and cortisol after dexamethasone administration during an asymptomatic period and was confirmed by pituitary imaging and by final histology after transphenoidal resection of the pituitary adenoma. After surgery, the patient resumed a normal pituitary-adrenal function with restoration of the normal ACTH and cortisol suppression after dexamethasone. Cyclic Cushing's disease should be considered in the differential diagnosis of several conditions characterised by recurrent episodes of idiopathic edema, hypokalemia or unexplained cardiac arrhythmia. In such patients, the pituitary-adrenal axis should be tested possibly during the acute phase of their disease or using the dexamethasone suppression test during asymptomatic intervals.

Presurgical serum thyroglobulin has no prognostic value in papillary thyroid cancer

We investigated whether serum thyroglobulin determination before surgery for differentiated thyroid carcinoma may have any prognostic value with regard to tumour extension and disease outcome in a retrospective series of 71 patients with papillary thyroid cancer. Presurgical serum thyroglobulin levels were correlated with the size of the primary tumoral nodule (p = 0.006) and of the whole thyroid (p = 0.02). The same correlation was found in a control group of patients with benign thyroid nodules, confirming that presurgical serum thyroglobulin cannot be used for the differential diagnosis of thyroid carcinoma. Presurgical serum thyroglobulin levels did not differ among patients with tumor limited to thyroid gland or extending to cervical lymph nodes or invading outside the thyroid capsule or metastasising to distant size. In addition presurgical serum thyroglobulin levels were not correlated with the disease outcome after a mean follow-up of 9 years: no difference was found among patients in complete remission or with persistent disease or dead from thyroid cancer. In conclusion, this study failed to show any prognostic value of presurgical serum thyroglobulin determination that consequently should not be measured.

Influence of human body composition on serum peak thyrotropin (TSH) after recombinant human TSH administration in patients with differentiated thyroid carcinoma

OBJECTIVES

In this study, we evaluated the influence of height, weight, body mass index (BMI), body surface area, and body composition [total lean body mass (LBM) and fat body mass] on serum peak TSH levels obtained after recombinant human (rh)TSH. Furthermore, to verify whether the serum peak TSH influenced the efficacy of radioiodine ((131)I), we compared the rate of thyroid remnant ablation according to the patients' BMI.

PATIENTS

We studied 105 patients with differentiated thyroid carcinoma who underwent rhTSH stimulation test. Serum TSH measurements were performed before and 24, 48, and 72 h after rhTSH administration. We also compared the rate of thyroid remnant ablation among 70 differentiated thyroid carcinoma patients with different BMI.

RESULTS

The serum peak TSH after rhTSH was significantly lower in overweight and obese subjects compared with normal-weight subjects (92.1 +/- 41.8, 82.4 +/- 24.2, and 112.7 +/- 46.3 microU/ml, respectively; P = 0.01) and in males compared with females (74.6 +/- 22.3 and 105.0 +/- 43.0 microU/ml, respectively; P = 0.0002). By univariate analysis, serum peak TSH was negatively related to weight, height, body surface area, BMI, LBM, and fat body mass, but only LBM was independently associated with serum peak TSH levels. Although it was confirmed that overweight and obese patients had a lower serum peak TSH, the rate of ablation did not differ among normal-weight, overweight, and obese patients.

CONCLUSIONS

With this study we demonstrated that LBM is the only parameter independently associated with serum peak TSH after rhTSH administration. However, the serum peak TSH does not influence the rate of (131)I remnant ablation.

All-trans-retinoic acid treatment inhibits the growth of retinoic acid receptor beta messenger ribonucleic acid expressing thyroid cancer cell lines but does not reinduce the expression of thyroid-specific genes

Conventional chemotherapy and radiotherapy are ineffective for the treatment of advanced thyroid tumors like poorly differentiated papillary, anaplastic, and medullary thyroid cancer. In the attempt to evaluate the possibility of using retinoic acid (RA) in the treatment of thyroid cancer refractory to conventional therapy, we studied the effect of all-trans-RA treatment on five human thyroid cancer cell lines. We found that WRO and NPA, derived from follicular and poorly differentiated human thyroid carcinoma, respectively, showed a growth inhibition after 25 and 21 d of RA treatment. Both apoptosis and a decrease in DNA synthesis were observed as mechanisms of growth inhibition. In the NPA cell line, a delay of cell-cycle progression has also been observed. On the contrary, we did not observe any recovery of mRNA expression of thyroid-specific genes and in particular of the sodium iodide symporter gene. The lack of recovery of radioiodide uptake after all-trans-RA treatment confirmed the inability to reexpress sodium iodide symporter mRNA. The main difference between the all-trans-RA responding cells (WRO and NPA) and the nonresponding cells [ARO, FRO (derived from human anaplastic thyroid tumors) and TT (derived from human medullary thyroid tumor)] was the basal and all-trans-RA induced RA receptor (RAR)beta mRNA expression. Interestingly, 14 thyroid tumors (10 papillary and four anaplastic) showed a significant lower expression of RARbeta mRNA when compared with normal thyroid tissues. In agreement with this result, only 30% of papillary thyroid carcinomas analyzed were positive for RARbeta protein expression with a degree of expression that was much lower than that found in normal thyroid tissue. In conclusion we found that all-trans-RA treatment can determine a significant in vitro growth inhibition especially in differentiated thyroid tumor-derived cell lines but it seems unable to reinduce the expression of thyroid-specific genes and in particular to reinduce the ability to take up iodine. The growth inhibition is likely due to apoptosis in an early phase and to a decrease of DNA synthesis later. In some cases, a delay of the cell-cycle progression also may be responsible for the growth inhibition. The finding of a basal and RA-induced RARbeta mRNA expression only in cell lines responding to all-trans-RA suggests that the growth inhibition might be mediated by RARbeta.

rhTSH-aided radioiodine ablation and treatment of differentiated thyroid carcinoma: a comprehensive review

Traditionally, withdrawal of thyroid hormone has been used to attain the increase in serum TSH concentrations that are believed to optimize the trapping and retention of radioiodine for diagnostic procedures, thyroid remnant ablation and treatment of patients with differentiated thyroid cancer (DTC). However, withdrawal frequently causes clinical hypothyroidism, with resultant cognitive impairment, emotional dysfunction, physical discomfort, health risks in patients who are elderly, frail or have concomitant illness, and impaired quality of life and ability to work. Recombinant human TSH (rhTSH) was developed to provide TSH stimulation without withdrawal of thyroid hormone and the associated morbidity. rhTSH has been approved as an adjunct for diagnostic procedures in patients with DTC, but is currently an experimental aid in thyroid remnant ablation and the treatment of thyroid tumours. In the period 1997-2004, nearly 30 medical centres worldwide have reported on almost 400 patients with DTC who were given rhTSH in preparation for radioiodine ablation of thyroid remnants or treatment of local tumours of metastatic disease. We have analysed and summarized the findings reported in this literature. Ablation aided by the standard course of rhTSH, two consecutive daily injections of 0.9 mg, had success rates better than 84% in 90 patients given radioiodine activities in excess of 4000 MBq. However, when 1110 MBq was administered, success rates were 81.2% in 16 patients given the standard course of rhTSH and 4-day withdrawal of thyroid hormone around the time of radioiodine administration in one study, but 54% in 70 patients in another study. rhTSH-aided treatment of persistent or recurrent local or metastatic cancer, or both, with from one to six courses of radioiodine 1000-19055 MBq, achieved 2% complete remission, 36% partial response and 27% disease stabilization rates, for a 65% clinical benefit rate, in 115 primarily elderly, late-stage patients for whom responses were reported. Twelve of these patients died as a result of progressive disease or were discharged from hospital into hospice care. Generally, rhTSH was very well tolerated. However, in a minority of patients with central nervous system, spinal or bone metastases, or bulky thyroid remnant or neck lesions with or without poor pulmonary reserve, administration of rhTSH, like thyroid hormone withdrawal, was found to stimulate expansion of the tumour, with ensuing compression of key anatomical structures and neurological, respiratory or other clinical complications. The rapid onset, response to glucocorticoids and radiological findings of peritumoural oedema or, less commonly, haemorrhage in the published cases, strongly suggest that the tumour expansion was the result of swelling rather than growth. As in the case of thyroid hormone withdrawal, special attention and glucocorticoid premedication are thus warranted when rhTSH is given to patients known or suspected to have the above characteristics. Dosimetric data suggest that whole-body and whole-blood radioiodine clearance may be faster in euthyroid patients after administration of rhTSH. In theory, the faster clearance could allow, or demand, increased radioiodine activities when rhTSH is used, but clinical data to date suggest that this may be unnecessary. The faster clearance also might result in safety or convenience benefits with the use of rhTSH, such as decreased exposure of extrathyroid areas to radiation, and shorter hospital stays. In conclusion, in preliminary results from open-label studies, both rhTSH-aided tumour ablation and treatment have been well tolerated and have shown efficacy in substantial proportions of patients. rhTSH-aided ablation merits further study. rhTSH-aided treatment may be preferred in patients who are at greater risk of hypothyroid complications from withdrawal of thyroid hormone or are unable to produce sufficient endogenous TSH, and warrants additional investigation in younger patients at earlier stages of thyroid cancer.

Follow-up and management of differentiated thyroid carcinoma: a European perspective in clinical practice

As differentiated (follicular and papillary) thyroid cancer (DTC) may recur years after initial treatment, follow-up of patients with DTC is long term. However, this population has changed, with more individuals being discovered at an earlier stage of disease, so that previous follow-up protocols based mostly on data from high-risk patients no longer apply. We have proposed, in a previous issue of this Journal, an improved protocol for the follow-up of low-risk patients with DTC based on the findings of recent studies. We report here the case of a paradigmatic patient with papillary thyroid carcinoma, with the goal of illustrating the benefits of applying this algorithm in routine clinical practice. We also offer expanded and additional comments on various issues in the management of DTC.

Medullary and papillary tumors are frequently associated in the same thyroid gland without evidence of reciprocal influence in their biologic behavior

Papillary thyroid microcarcinoma (mPTC), is a very frequent incidental finding with a frequency varying from a few percent to 35% at postmortem histopathologic examinations. However, the presence of mPTC in patients undergoing thyroidectomy for multinodular goiter (MNG) and for Graves' disease (GD) has been found to be lower. Patients with medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) association have been published as anecdotal case reports, as well as kindred with familial MTC or multiple endocrine neoplasia (MEN) 2A with some members simultaneously affected by MTC and PTC. We studied the prevalence and the biological behavior of MTC associated with PTC, with particular attention to those cases in which a mPTC was incidentally found. Twenty-seven of 196 (13.8%) MTC cases showed an association with PTC and in particular 21 of 190 (11.05%) with an incidental mPTC. This percentage is higher than that reported in the literature on the association of mPTC with GD (2.8%-4.5%) and MNG (3%). Also the percentage of the more general association of MTC/PTC, not restricted to mPTC, found in our series (13.8%) is higher than that reported in studies that analyzed the prevalence of PTC (any size) in patients treated for MNG (7.5%). A similarly high percentage of MTC/PTC had not been reported before and in particular there are no reports on large series of MTC/PTC. We also analyzed the epidemiologic, clinical, and pathologic features of MTC associated and not associated with PTC without finding any difference. In particular the outcome of the MTC did not appear to be influenced by the presence of the PTC and the specific radioiodine treatments. Moreover, although we cannot completely exclude a shared pathogenic event as the cause of both MTC and PTC, the molecular analysis of RET gene alterations did not show any common mutation.

Management of thyroid nodules: a clinicopathological, evidence-based approach

Management of thyroid nodules is one of the most controversial issues in thyroidology. Different approaches derive from geographical variation in presentation, inadequate or incomplete clinical diagnosis, lack of prospective controlled studies and, frequently, the different cultural backgrounds of physicians. This review aims to offer a practical approach to the management of nodular thyroid disorders, considering the way in which the pathophysiology of the disease provides clues to the correct clinical diagnosis and therapy.

RET exon 11 (G691S) polymorphism is significantly more frequent in sporadic medullary thyroid carcinoma than in the general population

The RET protooncogene is constitutively activated by point mutations in hereditary medullary thyroid carcinomas (MTCs). RET somatic point mutations have also been reported in 40-50% of sporadic MTCs. Several single nucleotide polymorphisms of the RET gene have been described in the general population as well as in patients with MTC. These allelic variants do not seem to confer any transforming activity to the tyrosine kinase domain of the RET gene. Because the exon 11 RET polymorphism determines an important aminoacidic variation (G691S), we studied its frequency in 212 subjects, 106 sporadic MTC patients and 106 normal age-, sex-, race-, and geographic origin-matched controls. In 46 cases of sporadic MTCs, we also studied the cosegregation of somatic RET gene mutation and G691S polymorphism as well as the linkage of the polymorphism with RET germline mutation in 60 members of eight multiple endocrine neoplasia type 2 families. The influence of this polymorphism on the RET gene transcription has also been studied. In parallel we analyzed the frequencies of another three neutral polymorphisms (L769L, S836S, S904S). We found a statistically significant (P = 0.029) higher allelic frequency of G691S polymorphism in MTCs (27.83%) than that found in normal controls (18.86%), at variance with the three neutral polymorphisms whose frequencies were not different in patients and controls. With this study we excluded the influence of the G691S polymorphism on RET mRNA expression, the development of the somatic RET mutation, the linkage with the germline RET mutation, the younger onset of the MTCs, and the clinical outcome of the disease. A putative role of the G691S polymorphism as genetic modifier in the normal subjects remains to be established.

BRAF(V599E) mutation is the leading genetic event in adult sporadic papillary thyroid carcinomas

Activating mutations of BRAF have been identified in a variety of human cancers, most notably melanomas and papillary thyroid carcinomas (PTCs). The aim of the present study was to disclose the role of BRAF mutations in thyroid carcinoma development. Seventy-two thyroid tumors, including 60 PTCs, six follicular adenomas, five follicular carcinomas, and one anaplastic carcinoma, were studied. BRAF mutation screening focused on exon 15 and exon 11 of the gene by single-stranded conformational polymorphism and sequence analysis. Search of RET/PTC expression was conducted with the RT-PCR technique. The molecular genetic study of the BRAF gene showed the presence of a missense thymine to adenine transversion at nucleotide 1796, resulting in the V599E substitution, in 24 of 60 PTCs (40%), none of six follicular adenomas, and none of five follicular carcinomas or one anaplastic carcinoma. Moreover, nine of 60 PTCs (15%) presented RET/PTC expression. A genetico-clinical association analysis showed a statistically significant correlation between BRAF mutation and development of PTCs of the classic papillary histotype (P = 0.038). On the contrary, no link could be detected between expression of BRAF(V599E) and age at diagnosis, gender, dimension, and local invasiveness of the primary cancer, presence of lymph node metastases, tumor stage, and multifocality of the disease. These data clearly confirm that BRAF(V599E) is the more common genetic alteration found to date in adult sporadic PTCs, that it is unique for this thyroid cancer histotype, and that it might drive the development of PTCs of the classic papillary subtype.

Follow-up of low-risk patients with differentiated thyroid carcinoma: a European perspective

OBJECTIVE

Because differentiated (follicular and papillary) thyroid cancer (DTC) may recur years after initial treatment, the follow-up of patients with DTC is long term. However, this population has changed, with more individuals being discovered at an earlier stage of the disease, so that previous follow-up protocols based mostly on data from high-risk patients no longer apply. We sought to develop an improved protocol for the follow-up of low-risk patients with DTC based on the findings of recent studies.

METHODS

We analysed recent literature on the follow-up of DTC.

RESULTS

Recent large studies have produced three important findings: (i) in patients with low-risk DTC with no evidence of disease up to the 6- to 12-month follow-up, diagnostic whole-body scan adds no information when serum thyroglobulin (Tg) is undetectable and interference from anti-Tg antibodies is absent; (ii) use of recombinant human thyroid-stimulating hormone to aid Tg measurement is effective and provides greater safety, quality-of-life and work productivity than does levothyroxine withdrawal with its attendant hypothyroidism; and (iii) ultrasonography performed by an experienced operator is the most sensitive means of detecting neck recurrences of DTC.

CONCLUSIONS

We present a revised follow-up protocol for low-risk patients taking into account the above findings. This protocol should help clinicians enter a new era of monitoring characterized by greater safety, simplicity, convenience and cost savings.

Low specificity of blood thyroglobulin messenger ribonucleic acid assay prevents its use in the follow-up of differentiated thyroid cancer patients

Thyroglobulin (Tg) is a glycoprotein specifically synthesized by follicular thyroid epithelium. After thyroidectomy and remnant (131)I ablation, serum Tg is a specific and sensitive marker for the presence of thyroid cancer tissue, and its measurement is fundamental in the follow-up of patients affected by differentiated thyroid carcinomas (DTCs), being even more sensitive than diagnostic whole-body scan. Unfortunately, serum Tg measurement becomes useless in approximately 15-25% of DTC cases who are positive for anti-Tg antibodies that interfere with the Tg measurement. In these cases, Tg mRNA measurement has been proposed as an alternative to serum Tg determination. The aim of this study was to verify the sensitivity and specificity of Tg mRNA measurement, performed by quantitative real-time RT-PCR, in a series of 100 subjects (80 DTC patients and 20 controls). From our data, the sensitivity and the specificity of the blood Tg mRNA measurement are 82.3 and 24.2%, respectively, with a positive predictive value and a negative predictive value of 65.6 and 43.7%, respectively. The comparison of the Tg mRNA with the serum Tg, measured by both chemiluminescent and ultrasensitive ELISA methods, confirmed the low specificity of the Tg mRNA assay. The hypothesis that Tg mRNA detectable levels could be predictive of future recurrences is not supported by the long follow-up (median, 7 yr; range, 3-29 yr) of our disease-free patients, who did not develop any recurrences in their clinical history. Moreover, nine disease-free patients, who showed positive levels of Tg mRNA (11.8-336 pg equivalents/ micro g RNA), were confirmed to be serum Tg free, both in basal conditions and after recombinant human TSH stimulation, 4 yr after the Tg mRNA detection. In conclusion, we demonstrated that the Tg mRNA assay is of poor utility in the follow-up of DTC patients. On the contrary, serum Tg measurement is a very sensitive and specific thyroid tumor marker, and we recommend that the follow-up of patients affected by DTC must be performed using serum Tg rather than blood Tg mRNA measurement.

Impact of routine measurement of serum calcitonin on the diagnosis and outcome of medullary thyroid cancer: experience in 10,864 patients with nodular thyroid disorders

The survival rate of patients with medullary thyroid carcinoma (MTC) is significantly better in patients diagnosed and treated when the tumor is limited to the thyroid. In a pioneer study carried out in 1991, we demonstrated that routine measurement of serum calcitonin (CT) in nodular thyroid disease allowed the preoperative diagnosis of unsuspected sporadic MTC with better accuracy than routine fine needle aspiration cytology (FNAC). This finding has been confirmed in subsequent studies. In the present study we report the results of CT screening in 10,864 patients with thyroid nodular disease seen in the years 1991-1998 (group 1). We analyzed the prevalence of MTC and compared their outcomes with those of a historical group of patients (group 2) diagnosed before the introduction of CT screening (1970-1990). The prevalence of MTC found by CT screening in group 1 was 0.40% (44 patients). A positive CT test had a higher diagnostic sensitivity and specificity compared with FNAC. CT screening allowed the diagnosis of MTC at an earlier stage compared with group 2 (P = 0.004). Normalization of serum CT levels (undetectable) after surgery was more frequently observed in group 1. At the end of follow-up, complete remission was observed in 59% of group 1 and in 2.7% of group 2 (P = 0.0001). Our study confirms that MTC is not an infrequent finding among patients with thyroid nodules (nearly 1 in 250 patients). In addition, screening thyroid nodules with serum CT measurement allows the diagnosis and treatment of MTC at an earlier stage, resulting in a better outcome compared with MTC not detected by serum CT measurement. One of the reasons for this finding is that increasing the preoperative diagnostic accuracy of MTC prompts the surgeon to perform a more radical and possibly curative treatment. On this basis, routine measurement of basal serum CT levels should be considered an integral part of the diagnostic evaluation of thyroid nodules.

Disappearance of humoral thyroid autoimmunity after complete removal of thyroid antigens

BACKGROUND

The development of antibodies to thyroid peroxidase, thyroglobulin, and thyroid-stimulating hormone (TSH) receptor is a main feature of autoimmune thyroid diseases.

OBJECTIVE

To investigate whether complete removal of thyroid antigens results in the abatement of humoral thyroid autoimmunity.

DESIGN

Retrospective chart review study of patients treated and monitored with a standard prospective protocol.

SETTING

University hospital in Pisa, Italy, between 1976 and 1994.

PATIENTS

182 patients with differentiated thyroid carcinoma and serum antibodies to thyroid peroxidase, thyroglobulin, or TSH receptor due to coexistent clinical Hashimoto thyroiditis, Graves disease, or focal autoimmune thyroiditis.

INTERVENTION

Total thyroidectomy and radioiodine treatment to ablate residual or metastatic thyroid tissue. Regular follow-up with iodine-131 whole-body scanning and serum thyroglobulin measurement. Mean follow-up (+/-SD) was 10.1 +/- 4.1 years (range, 4 to 20 years).

MEASUREMENTS

Serum antibodies to thyroid peroxidase, thyroglobulin, and TSH receptor.

RESULTS

Thyroid peroxidase, thyroglobulin, and TSH-receptor antibodies progressively disappeared after the initial treatment. The median disappearance time was 6.3 years for thyroid peroxidase antibodies and 3.0 years for thyroglobulin antibodies. There was a statistically significant correlation between the disappearance of thyroid tissue and that of thyroid antibodies. The coexistence of Hashimoto thyroiditis or Graves disease with thyroid cancer did not modify the pattern of disappearance of thyroid antibody compared with patients with focal autoimmune thyroiditis.

CONCLUSIONS

Complete ablation of thyroid tissue with its antigenic components results in the disappearance of antibodies to all major thyroid antigens, thus supporting the concept that continued antibody production depends on the persistence of autoantigen in the body.

Biology and clinical application of the NIS gene

The sodium iodide symporter (NIS) is a plasma basolateral membrane protein that actively transports iodide to the thyroid follicular cells as the first step of thyroid hormone biosynthesis. NIS also mediates active iodide transport in other human tissues including the salivary glands, lactating mammary gland and gastric mucosa. NIS expression has been recently reported also in several other human tissues but its physiological role is still unclear. Cloning of the NIS gene and the development of specific NIS antibodies have allowed the characterization of the pathogenic role of NIS in thyroid cancer, thyroid autoimmune diseases, congenital hypothyroidism and other, non-thyroidal human diseases. The possibility to increase its levels of expression or to reinduce its expression in thyroid carcinomas that have lost the ability to take up radioiodine is one of the most promising clinically related fields of research. The recent discovery that more than 80% of human breast carcinomas endogenously express NIS protein has opened a very interesting new area of research into the possibility of using radioiodide in the diagnosis and treatment of breast cancer. In an attempt to make tumor cells susceptible to radioiodide destruction, several types of cancer cells have been transfected with the NIS gene. This has demonstrated the feasibility of the in vitro technique but also raised the problem of the absence of the iodide organification machinery in non-thyroidal cells, which, at the moment, represents the major limit of this strategy.

Recombinant human thyrotropin-stimulated serum thyroglobulin combined with neck ultrasonography has the highest sensitivity in monitoring differentiated thyroid carcinoma

Recombinant human TSH (rhTSH)-stimulated thyroglobulin (Tg) measurement and (131)I whole body scan (WBS) have been validated as informative tests in the postsurgical follow-up of differentiated thyroid carcinoma. We report the diagnostic accuracy of Tg measurement and diagnostic WBS, alone or in combination, after rhTSH stimulation in a retrospective, consecutive series of patients undergoing follow-up for differentiated thyroid cancer. Routine procedures also include neck ultrasound in every patient and post-therapy WBS when indicated. We studied 340 consecutive patients with differentiated thyroid carcinoma, previously treated with near-total thyroidectomy and (131)I thyroid ablation, scheduled for routine diagnostic tests. At baseline on L-T(4)-suppressive therapy, 294 patients had undetectable (<1 ng/ml) serum Tg and negative anti-Tg autoantibodies (TgAb), 25 patients had undetectable serum Tg and positive TgAb, and 21 patients had detectable serum Tg and negative TgAb. These patients were tested for the presence of active disease by rhTSH stimulation. The results of our study showed that rhTSH-stimulated Tg alone had a diagnostic sensitivity of 85% for detecting active disease and a negative predictive value (NPV) of 98.2%. After adding the results of neck ultrasound, sensitivity increased to 96.3%, and the NPV to 99.5%. rhTSH-stimulated WBS had a sensitivity of only 21% and a NPV of 89%. The combination of rhTSH-stimulated Tg and WBS had a sensitivity of 92.7% and a NPV of 99%. We conclude that the rhTSH-stimulated Tg test combined with neck ultrasonography has the highest diagnostic accuracy in detecting persistent disease in the follow-up of differentiated thyroid carcinoma. A detectable level of serum Tg on L-T(4), its conversion from undetectable to detectable after rhTSH, and/or a suspicious finding at ultrasound will allow the identification of patients requiring therapeutic procedures without the need for diagnostic WBS.

The effect of short-term treatment with recombinant human thyroid-stimulating hormones on leydig cell function in men

High levels of thyroid-stimulating hormone (TSH) have been implicated as a cause for precocious puberty associated with severe long-standing juvenile hypothyroidism. Recombinant human thyroid-stimulating hormone (rhTSH) is available for the management of patients with thyroid carcinoma, and after its administration the serum TSH levels are similar to those observed in hypothyroid infants with precocious puberty. Our objective was to investigate whether rhTSH increased testosterone secretion in adult males with differentiated thyroid carcinoma. Thirty-one adult Caucasian men, ages 18-59 years, with differentiated thyroid carcinoma were studied. While continuing on thyroid hormone therapy, patients received 0.9 mg of rhTSH 24 hours apart. Blood samples were obtained before the first rhTSH dose (day 1) and at 24 hours (day 3) and 72 hours (day 5) after the second rhTSH dose. TSH, total testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were determined. Serum TSH levels were increased at day 3 (129.2 +/- 5.7 micro U/mL) versus day 1 (0.6 +/- 0.2 micro U/mL) but observed differences in total testosterone, LH and FSH throughout the study were not statistically significant. In conclusion, short-term elevations in serum TSH levels in the range reported in hypothyroid boys with precocious puberty did not increase serum testosterone levels in adult men.

Video-assisted surgery of the thyroid diseases

BACKGROUND

After first endoscopic parathyroidectomy, performed and described by Gagner in 1996, several surgeons reported their experiences with minimally invasive and video-assisted (MIVA) surgery of the neck. The patients were considered eligible for MIVA hemithyroidectomy and thyroidectomy on the basis of some criteria.

METHODS

Completely gasless procedure, is carried out through a 15-30 mm central incision above the sternal notch. Dissection is performed mainly under endoscopic vision using conventional endoscopic instruments. Video assisted group in our experience included 5 patients. All patients were women with mean age of 56 years.

RESULTS

We performed in three cases a total thyroidectomy and in two an hemithyroidectomy. Operative mean time was 189 minutes. No complications are happened. No conversion have been necessary.

DISCUSSION

Traditionally, open thyroidectomy require a 6 to 8 cm, or bigger, transverse wound on the lower neck. The minimally invasive approach wound is very small in length (1.5 cm for small nodules, maximum 2-3 cm for the biggest, in respect of the exclusion criteria) upon the suprasternal notch. Wound pain following the MIVA surgery is much less when compared with the conventional thyroidectomy, because there is less dissection and destruction of tissues. The treated pathologies are prevalently nodular goiter; the only kind of thyroid cancer what it may be attacked with endoscopic surgery is a small papillary carcinoma without lymph node involvement. The complications, there are the same complications of the traditional thyroidectomy. Conversion to the traditional approach sometimes may it be required.

CONCLUSIONS

At the present this kind of surgery, in selected patients, clearly demonstrate excellent results regarding patient cure rate and comfort, with short hospital stay, few postoperative pain and attractive cosmetic results.

A consensus report of the role of serum thyroglobulin as a monitoring method for low-risk patients with papillary thyroid carcinoma

Recent studies have provided new information regarding the optimal surveillance protocols for low-risk patients with differentiated thyroid cancer (DTC). This article summarizes the main issues brought out in a consensus conference of thyroid cancer specialists who analyzed and discussed this new data. There is growing recognition of the value of serum thyroglobulin (Tg) as part of routine surveillance. An undetectable serum Tg measured during thyroid hormone suppression of TSH (THST) is often misleading. Eight studies show that 21% of 784 patients who had no clinical evidence of tumor with baseline serum Tg levels usually below 1 micro g/liter during THST had, in response to recombinant human TSH (rhTSH), a rise in serum Tg to more than 2 micro g/liter. When this happened, 36% of the patients were found to have metastases (36% at distant sites) that were identified in 91% by an rhTSH-stimulated Tg above 2 micro g/liter. Diagnostic whole body scanning, after either rhTSH or thyroid hormone withdrawal, identified only 19% of the cases of metastases. Ten studies comprising 1599 patients demonstrate that a TSH-stimulated Tg test using a Tg cutoff of 2 micro g/liter (either after thyroid hormone withdrawal or 72 h after rhTSH) is sufficiently sensitive to be used as the principal test in the follow-up management of low-risk patients with DTC and that the routine use of diagnostic whole body scanning in follow-up should be discouraged. On the basis of the foregoing, we propose a surveillance guideline using TSH-stimulated Tg levels for patients who have undergone total or near-total thyroidectomy and (131)I ablation for DTC and have no clinical evidence of residual tumor with a serum Tg below 1 micro g/liter during THST.

Simian virus 40-like sequences from early and late regions in human thyroid tumors of different histotypes

Simian virus 40 (SV40) sequences were investigated in human thyroid tumors of different histotypes, Graves' disease thyroid specimens, normal thyroid tissues, and peripheral blood mononuclear cells (PBMC) of healthy donors. Specific SV40 large T antigen (Tag) sequences were detected, by PCR and filter hybridization, in human thyroid tumors with a frequency ranging from 66% in papillary thyroid carcinomas (PTC) to 100% in anaplastic thyroid carcinomas (ATC). SV40 was revealed in 60% and 100% of normal thyroid tissues adjacent to PTC and ATC, respectively, but in only 10% of control normal thyroid tissues (NTT) from patients affected by multinodular goiter. Thyroid tissues from patients affected by the Graves' disease were found to be SV40 positive with a frequency of 20%. In agreement with previous investigations, the presence of SV40 sequences was detected in 25% of PBMC of healthy individuals. SV40 Tag mRNA was detected by RT-PCR, whereas the viral oncoprotein was revealed by immunohistochemistry with a specific monoclonal antibody. The high prevalence of SV40 footprints in human thyroid tumors indicates that the oncogenic virus may participate as a cofactor in the onset/progression of specific human thyroid cancers. Detection of SV40 sequences in NTT adjacent to thyroid cancers suggests that the viral infection may spread from transformed cells to normal cells surrounding the tumor. The presence of the SV40 footprint in PBMC implies that blood cells are vectors of the virus in other tissues of the host.

Minimally invasive video-assisted thyroidectomy for papillary carcinoma: a prospective study of its completeness

BACKGROUND

The effectiveness of minimally invasive video-assisted thyroidectomy (MIVAT) in papillary thyroid carcinoma is still debated. Some are concerned about this procedure in patients with thyroid cancer. This prospective study aimed to demonstrate that near-total thyroidectomy can be performed by MIVAT with similar results compared with open thyroidectomy.

METHODS

A total of 33 patients with a thyroid nodule proven to be a papillary thyroid carcinoma underwent a near-total thyroidectomy. They were randomly assigned to group A (n = 16) or group B (n = 17) who were treated either by MIVAT or conventional near-total thyroidectomy, respectively. Iodine-131 thyroid bed uptake and serum thyroglobulin were measured 1 month after operation. Data were analyzed by unpaired t test and Mann-Whitney statistic methods.

RESULTS

. Mean iodine-131 uptake was 5.1 +/- 4.9% in group A and 4.6 +/- 6.7% in group B. Mean thyroglobulin serum levels were 5.3 +/- 5.8 ng/mL in group A and 7.6 +/- 21.7 ng/mL in group B. The differences were not statistically significant.

CONCLUSIONS

The results of this study showed that the completeness obtained with MIVAT is similar to that obtained with open thyroidectomy, with the great advantage of a minimal neck wound. No conclusions can be drawn in terms of influence of MIVAT on the outcome of the patients with small papillary thyroid carcinoma.

Cytotoxic effects of carboplatinum and epirubicin in the setting of an elevated serum thyrotropin for advanced poorly differentiated thyroid cancer

Chemotherapy represents the only therapeutic option in most poorly differentiated thyroid carcinomas, although its effect is limited and short lasting. The aim of this study was to evaluate whether increasing the metabolic rate of thyroid cancer cells by TSH stimulation might result in higher response rate to chemotherapy. Fourteen patients with poorly differentiated thyroid carcinoma and nonfunctioning diffuse lung metastases detected at computed tomography scan, entered this study. A combination of carboplatinum and epirubicin was administered at 4- to 6-wk intervals for six courses. TSH stimulation was achieved by reduction of the daily dose of L-thyroxine resulting in mild hypothyroidism (eight patients) or by administration of recombinant human TSH (six patients). Two additional patients did not complete the therapeutic protocol due to severe hematological side effects. Results were evaluated by comparison of lung computed tomography scans before and after therapy. One patient had a complete remission. Five patients had partial remission, and seven patients had disease stabilization. One patient progressed to death. The overall rate of positive responses was 37% that rose to 81% when including patients with stable disease. Serum thyroglobulin after chemotherapy declined more than 50% in six patients, with respect to basal levels. Apparently, no difference in the response rate was observed between exogenous or endogenous TSH stimulation. At the time of this analysis, among the patients who completed the treatment courses, 9 of 14 patients (64.3%) are still alive (median survival from start of chemotherapy = 21 months, range: 15-34). Six of these patients did not show progression of lung disease, whereas regrowth of lung metastases was observed in three patients after 19, 20, and 21 months from chemotherapy, respectively. Five patients died of their disease, including the one who had progression of lung disease during chemotherapy, three who died for brain or bone metastases, and one who died for refractory local tumor invasion. No progression of lung metastases was observed until death in these four patients. In conclusion, the response rate of poorly differentiated thyroid cancer to chemotherapy observed in this study was favorable and promising. TSH stimulation may have contributed to these results.

Ablation of thyroid residues with 30 mCi (131)I: a comparison in thyroid cancer patients prepared with recombinant human TSH or thyroid hormone withdrawal

The aim of the study was to assess whether stimulation by recombinant human TSH (rhTSH) may be used in patients with differentiated thyroid carcinoma for postsurgical ablation of thyroid remnants using a 30-mCi standard dose of (131)I during thyroid hormone therapy. The rate of ablation was prospectively compared in three groups of patients consecutively assigned to one of three treatment arms: in the first arm, patients (n = 50) were treated while hypothyroid (HYPO); in the second arm, patients (n = 42) were treated while HYPO and stimulated in addition with rhTSH (HYPO + rhTSH); in the third arm, patients (n = 70) were treated while euthyroid (EU) on thyroid hormone therapy and stimulated with rhTSH (EU + rhTSH). The outcome of thyroid ablation was assessed by conventional HYPO (131)I scan performed in HYPO state 6-10 months after ablation. Basal serum TSH was elevated in the HYPO and HYPO + rhTSH groups. In the EU + rhTSH group, basal serum TSH was 1.3 +/- 2.5 micro U/ml (range, <0.005-11.9 micro U/ml). After rhTSH, serum TSH significantly increased in the HYPO + rhTSH group and the EU + rhTSH group. Basal 24-h radioiodine thyroid bed uptake was 5.8 +/- 5.7% (range, 0.2-21%) and 5.4 +/- 5.7% (range, 0.2-26%) in the HYPO and HYPO + rhTSH groups, respectively. In the HYPO + rhTSH group, mean 24-h thyroid bed uptake rose to 9.4 +/- 9.5% (range, 0.2-46%) after rhTSH (P < 0.0001). The 24-h uptake after rhTSH in the EU + rhTSH group was 2.5 +/- 4.3% (range, 0.1-32%), significantly lower (P < 0.0001) than that found in the HYPO and HYPO + rhTSH groups. The rate of successful ablation was similar in the HYPO and HYPO + rhTSH groups (84% and 78.5%, respectively). A significantly lower rate of ablation (54%) was achieved in the EU + rhTSH group. Mean initial dose rate (the radiation dose delivered during the first hour after treatment) was significantly lower in the EU + rhTSH group (10.7 +/- 12.6 Gy/h) compared with the HYPO + rhTSH group (48.5 +/- 43 Gy/h) and the HYPO group (27.1 +/- 42.5 Gy/h). In conclusion, our study indicates that by using stimulation with rhTSH, a 30-mCi standard dose of radioiodine is not sufficient for a satisfactory thyroid ablation rate. Possible reasons for this failure may be the low 24-h radioiodine uptake, the low initial dose rate delivered to the residues, and the accelerated iodine clearance observed in EU patients. Possible alternatives for obtaining a satisfactory rate of thyroid ablation with rhTSH may consist of increasing the dose of radioiodine or using different protocols of rhTSH administration producing more prolonged thyroid cells stimulation.

Follow-up of differentiated thyroid cancer

The aim of post-surgical follow-up for differentiated thyroid carcinoma is the early identification of the small proportion of patients who have residual disease or develop a recurrence. When total thyroidectomy and radioiodine ablation have been the initial treatment, three powerful tools are available for the follow-up: basal and TSH-stimulated serum thyroglobulin (Tg) measurement, iodine-131 whole body scan (WBS) and neck ultrasound. Serum Tg measurement is the most sensitive and specific marker of differentiated thyroid cancer. Undetectable serum Tg levels are found in the large majority of disease-free patients, while elevated concentrations of serum Tg are associated with the presence of residual or metastatic thyroid tissue. In the last case, WBS under TSH stimulation (either after withdrawal of L-thyroxine therapy or after recombinant human TSH stimulation) and neck ultrasound are the most informative tests for the detection of distant or local metastases, respectively, that require more appropriate treatment (surgery and/or radioiodine therapy). Using this strategy, most patients will achieve definitive cure and will have a normal quality of life.

Diagnostic 131-iodine whole-body scan may be avoided in thyroid cancer patients who have undetectable stimulated serum Tg levels after initial treatment

The follow-up of differentiated thyroid cancer after total thyroidectomy and thyroid ablation is commonly based on serum Tg determination and 131-iodine ((131)I) diagnostic whole-body scan (WBS) performed in the hypothyroid state, 6-12 months after thyroid ablation. Based on the greater sensitivity of Tg measurement, with respect to WBS, the diagnostic yield of diagnostic WBS has been questioned in patients who are off L-T(4) therapy and have undetectable Tg levels. The aim of the present retrospective study was to evaluate the diagnostic relevance of (131)I WBS performed after thyroid remnant ablation, in patients with undetectable serum Tg and off thyroid hormone therapy. The study included 315 of 662 consecutive patients (47.6%) treated in our department between 1980 and 1990, who, at the first control WBS after thyroid ablation, had undetectable serum Tg levels in the hypothyroid state. There were 54 men (17%) and 261 women (83%), with a mean age of 40.9 +/- 13.1 yr (range, 12-76), followed for a mean of 12 +/- 2.8 (range, 9-19) yr. The control WBS was negative in 225 (71.4%) patients and positive for persistent areas of thyroid bed uptake, frequently of very low significance, in 90 (28.6%). No local or distant metastases were discovered. At the last follow-up visit (1999-2000), 281 (89.2%) patients showed complete remission, with undetectable serum Tg off L-T(4) and negative WBS. Persistent thyroid bed uptake, with undetectable levels of Tg, was observed in 29 patients (9.2%) studied during L-T(4) withdrawal. Only 2 patients (0.6%) experienced local recurrence (lymph-node metastases) during their follow-up. In conclusion, our data suggest that the presence of undetectable levels of serum Tg off L-T(4) at the time of the first control WBS after initial treatment, is highly predictive of complete and persistent remission. With the exception of detecting persistent thyroid bed uptake in a minority of cases, the control WBS has never given information that could influence the following therapeutic strategy. On this basis, we propose that the diagnostic (131)I WBS may be avoided in patients with undetectable levels of Tg off L-T(4). These patients may be monitored with clinical examination, neck ultrasound, and serum Tg measurements on L-T(4).

Establishment of a non-tumorigenic papillary thyroid cell line (FB-2) carrying the RET/PTC1 rearrangement

A novel human thyroid papillary carcinoma cell line (FB-2) has been established and characterized. FB-2 cells harbor the RET/PTC1 chimeric oncogene in which the RET kinase domain is fused to the H4 gene. FB-2 cells neither formed colonies in semisolid media nor induced tumors after heterotransplant into severe combined immunodeficient mice. However, HMGI(Y), HMGI-C and c-myc genes, which are associated to thyroid cell transformation, were abundantly expressed in FB-2 cells but not in normal thyroid cells. FB-2 cells only partially retained the differentiated thyroid phenotype. In fact, the PAX-8 gene, which codes for a transcriptional factor required for thyroid cell differentiation, was expressed, while thyroglobulin, TSH-receptor and thyroperoxidase genes were not. Moreover, FB-2 cells produced high levels of interleukin (IL)-6 and IL-8.

[Prophylactic total thyroidectomy in children and adolescents with genetic mutations in the RET-protooncogene]

Medullary thyroid cancer (C.M.T.) can be a sporadic form generally in adults or a heredofamilial form where the first symptom appears in pediatric and adolescent age. The hereditary form can be isolated or associated with others endocrine neoplasias of type 2: MEN2a (with or without cutaneous lichen amyloidosis) and MEN2b. The responsible gene of the transmission has been identified in proto-oncogene RET localized on chromosome 10. Point form mutations of this proto-oncogene have been found on exons 10 and 11 in MEN2a and on 16 in MEN2b. In our study on 64 subjects, who belong 11 familiar groups, affected by MEN2a, MEN2b and familiar C.M.T., underwent a genetic research to look for point form mutations of proto-oncogene RET with PCR followed by the analysis of restriction. A genetic mutation has been revealed in 25 subjects: 18 were already known affected by MEN2 and so surgical treated and 7 seemed healthy (mean age 17.4 years, range 10-25). These 7 patients has been undergone clinical research and surgical treatment: a total thyroidectomy associated a lymphectomy of the central compartment. In all cases the histological exam showed C.M.T. moreover a patient had metastasis in lymph nodes of the central compartment. Another had hyperparathyroidism and pheochromocytoma treated with total thyroidectomy, parathyroidectomy and bilateral laparoscopic adrenalectomy. The identification in a very early age of carrier subjects of hill's gene inside an affected family, permits the execution of a prophylactic total thyroidectomy to prevent the C.M.T.. The penetrance of this neoplasia in hereditary form is 100%.

Potent mitogenicity of the RET/PTC3 oncogene correlates with its prevalence in tall-cell variant of papillary thyroid carcinoma

The tall-cell variant (TCV) of papillary thyroid carcinoma (PTC), characterized by tall cells bearing an oxyphilic cytoplasm, is more clinically aggressive than conventional PTC. RET tyrosine kinase rearrangements, which represent the most frequent genetic alteration in PTC, lead to the recombination of RET with heterologous genes to generate chimeric RET/PTC oncogenes. RET/PTC1 and RET/PTC3 are the most prevalent variants. We have found RET rearrangements in 35.8% of TCV (14 of 39 cases). Whereas the prevalences of RET/PTC1 and RET/PTC3 were almost equal in classic and follicular PTC, all of the TCV-positive cases expressed the RET/PTC3 rearrangement. These findings prompted us to compare RET/PTC3 and RET/PTC1 in an in vitro thyroid model system. We have expressed the two oncogenes in PC Cl 3 rat thyroid epithelial cells and found that RET/PTC3 is endowed with a strikingly more potent mitogenic effect than RET/PTC1. Mechanistically, this difference correlated with an increased signaling activity of RET/PTC3. In conclusion, we postulate that the correlation between the RET/PTC rearrangement type and the aggressiveness of human PTC is related to the efficiency with which the oncogene subtype delivers mitogenic signals to thyroid cells.

Guidelines for diagnosis and therapy of MEN type 1 and type 2

This is a consensus statement from an international group, mostly of clinical endocrinologists. MEN1 and MEN2 are hereditary cancer syndromes. The commonest tumors secrete PTH or gastrin in MEN1, and calcitonin or catecholamines in MEN2. Management strategies improved after the discoveries of their genes. MEN1 has no clear syndromic variants. Tumor monitoring in MEN1 carriers includes biochemical tests yearly and imaging tests less often. Neck surgery includes subtotal or total parathyroidectomy, parathyroid cryopreservation, and thymectomy. Proton pump inhibitors or somatostatin analogs are the main management for oversecretion of entero-pancreatic hormones, except insulin. The roles for surgery of most entero-pancreatic tumors present several controversies: exclusion of most operations on gastrinomas and indications for surgery on other tumors. Each MEN1 family probably has an inactivating MEN1 germline mutation. Testing for a germline MEN1 mutation gives useful information, but rarely mandates an intervention. The most distinctive MEN2 variants are MEN2A, MEN2B, and familial medullary thyroid cancer (MTC). They vary in aggressiveness of MTC and spectrum of disturbed organs. Mortality in MEN2 is greater from MTC than from pheochromocytoma. Thyroidectomy, during childhood if possible, is the goal in all MEN2 carriers to prevent or cure MTC. Each MEN2 index case probably has an activating germline RET mutation. RET testing has replaced calcitonin testing to diagnose the MEN2 carrier state. The specific RET codon mutation correlates with the MEN2 syndromic variant, the age of onset of MTC, and the aggressiveness of MTC; consequently, that mutation should guide major management decisions, such as whether and when to perform thyroidectomy.

Prediction of disease status by recombinant human TSH-stimulated serum Tg in the postsurgical follow-up of differentiated thyroid carcinoma

Stimulation with recombinant human TSH (rhTSH) has been introduced in clinical practice as an effective alternative to thyroid hormone withdrawal for the diagnostic follow-up (Tg measurement and 131-iodine whole-body scan) of patients with differentiated thyroid cancer. The present study was specifically aimed to evaluate the utility of rhTSH-stimulated serum Tg measurements in patients with undetectable serum Tg values, on L-T(4) therapy, as the only test to differentiate patients with persistent disease from patients who are disease-free. We studied 72 consecutive patients with differentiated thyroid cancer, previously treated with near-total thyroidectomy and 131-I thyroid ablation. Admission criteria were: an undetectable (<1 ng/ml) serum Tg, on L-T(4) therapy, and negative anti-Tg antibodies. The study design consisted of a Tg-stimulation test after rhTSH, during L-T(4), followed by diagnostic WBS and serum Tg measurement off L-T(4). After rhTSH, serum Tg remained undetectable in 41 of 72 patients (56.9%). A negative rhTSH Tg test agreed with an undetectable hypo-Tg in 36 of 41 cases (87.8%), all without evidence of metastatic disease at hypo-WBS. In 5 of 41 cases (12.2%), hypo-Tg was detectable (1.1-7.8 ng/ml), in association with negative hypo-WBS or faint uptake in the thyroid bed. Serum Tg converted from undetectable to detectable after rhTSH in 31 of 72 patients (43.1%), with a peak Tg ranging between 1.2 and 23.0 ng/ml. Hypo-Tg was always detectable in these patients (100% concordance), and it was significantly higher than rhTSH-stimulated Tg (P < 0.0002). Hypo-WBS was positive in 23 of 31 patients (74.2%), showing thyroid residues in 12, cervical lymph nodes in 7, and lung metastases in 4 cases. In 8 of 31 cases, hypo-WBS was negative, despite detectable serum Tg. Thus, rhTSH-stimulated Tg was able to detect all cases of documented local or distant metastases. In conclusion, our data indicate that, in patients with undetectable basal levels of serum Tg, rhTSH-stimulated Tg represents an informative test to distinguish disease-free patients (not requiring WBS) from diseased patients (requiring further diagnostic and/or therapeutic procedures).

RET protein expression has no prognostic impact on the long-term outcome of papillary thyroid carcinoma

BACKGROUND

RET proto-oncogene rearrangements (RET/PTC) are causative events in the pathogenesis of a subset of papillary thyroid cancer (PTC). The prevalence of RET/PTC varies in different countries and according to specific clinical features: it is higher after radiation exposure and it is claimed to be higher in young patients. Conflicting results are reported regarding the prognostic role of RET/PTC activation.

OBJECTIVE

To investigate the prognostic meaning of RET/PTC rearrangement on the long term outcome of PTC.

METHODS

We have studied the expression of the RET encoded protein in 127 papillary thyroid carcinomas by immunohistochemistry using a polyclonal antibody against the tyrosine-kinase domain of the RET protein. These cases have been collected during 1970-1985, and have a mean (+/-S.D.) period of follow-up of 18.6+/-3.7 years (range 12-27 years). The results have been compared with the patients' outcome.

RESULTS

The tyrosine-kinase domain of RET was expressed in 82 (64.6%) papillary carcinomas. Among them, RET was highly expressed in 65 (51.2%) cases and moderately expressed in 17 (13.4%). RET expression was absent in 45 (35.4%) cases. No correlation was found between RET expression and other parameters such as sex, age at diagnosis, tumor class and histological variant. Follow-up analysis showed no influence of RET expression on patients' outcome. By multivariate analysis, age (>45 years) and tumor class IV, but not sex and RET expression were adverse prognostic indicators of death.

CONCLUSION

In conclusion, our analysis indicates that RET expression is frequently found in PTC, and has no influence on tumor outcome.

Contralateral papillary thyroid cancer is frequent at completion thyroidectomy with no difference in low- and high-risk patients

Total (or near-total) thyroidectomy (TT) is considered by many as the most adequate treatment for papillary thyroid carcinoma (PTC). In patients who have undergone lobectomy, the necessity of performing a completion thyroidectomy (CT) is still discussed. The aim of this retrospective study was to evaluate tumor bilaterality in patients initially treated with partial thyroidectomy for PTC and who then underwent CT. We studied 182 patients treated with CT after lobectomy and/or isthmectomy for PTC diagnosed from 1969-1998. Mean age at diagnosis was 40+/-14.5 years and mean interval between partial thyroidectomy and CT was 19.8+/-56.8 months. At CT, 80 of 182 patients (44%) had one or more foci of tumor in the remaining thyroid lobe, always of the same papillary histotype, associated with ipsilateral lymph node metastases in 22 cases. In addition, 10 patients with no tumoral foci in the thyroid specimen had evidence of lymph node metastases. The rate of bilateral tumor was not different when patients were analyzed according to the classification of "low-" or "high-risk." Among several clinical features, the presence of lymph node metastases at the first surgical treatment and time interval between first treatment and CT were correlated with higher frequency of bilaterality (p = 0.033 and p = 0.044, respectively). The postsurgical 131I whole-body scan revealed the presence of persistent lymph node metastases or diffuse micronodular lung metastases in 7 and 6 patients, respectively. In conclusion, PTC was frequently bilateral in our series and this bilaterality was independent from the "low-" or "high-risk" classification. On these bases, we believe that PTC should be treated with TT when diagnosed before surgery and submitted to CT, if partial surgery was the initial intervention.

Outcome of differentiated thyroid cancer with detectable serum Tg and negative diagnostic (131)I whole body scan: comparison of patients treated with high (131)I activities versus untreated patients

Detectable serum Tg levels associated with negative diagnostic (131)I whole body scan are not infrequently found in patients with differentiated thyroid cancer. Several researchers have shown that in these patients the administration of high (131)I activity (100 mCi or more) increases the sensitivity of a posttherapy diagnostic (131)I whole body scan performed a few days later and allows the detection of neoplastic foci not seen with diagnostic doses of (131)I. Empirical radioiodine treatment has also been advocated by some researchers, but its therapeutic effect is controversial. In our institute, positive serum Tg/negative diagnostic (131)I whole body scan patients were not treated with high (131)I activities before 1984; afterward, almost all patients with positive serum Tg/negative diagnostic (131)I whole body scan patients were treated with radioiodine, and a posttherapy diagnostic (131)I whole body scan was performed. In the present retrospective study we compared the outcome of these two groups of patients, 42 treated and 28 untreated, followed for mean periods of 6.7 +/- 3.8 and 11.9 +/- 4.4 yr, respectively. In the treated group the first posttherapy diagnostic (131)I whole body scan was negative in 12 patients and positive in 30 patients. (131)I treatment was further administered only in the latter group. At the end of follow-up in treated patients a complete remission (normalization of serum Tg off L-thyroxine and negative diagnostic (131)I whole body scan) was observed in 10 patients (33.3%). In 9 cases (30%) posttherapy diagnostic (131)I whole body scan became negative, and serum Tg was reduced but still detectable; in 11 patients (36.6%) serum Tg was detectable, and posttherapy diagnostic (131)I whole body scan was positive. The resolution of (131)I uptake in lung metastases was observed in 8 of 9 cases (88.8%) and in cervical node metastases in 11 of 18 cases (61.1%). In patients treated only once because the posttherapy diagnostic (131)I whole body scan was negative (n = 12), 2 patients (16.7%) were in apparent remission, 7 (58.3%) had detectable Tg values without evidence of disease, 2 (16.7%) showed lymph node metastases in the mediastinum, and 1 patient (8.3%) died because of lung metastases. Of the 28 untreated patients, none with radiological evidence of disease, serum Tg off L-thyroxine therapy became undetectable in 19 cases (67.9%), significantly reduced in 6 cases (21.4%), and unchanged or increased in 3 patients (10.7%), 1 of whom developed lung metastases 14 yr after the diagnosis. In summary, our results indicate that in patients with detectable serum Tg and negative diagnostic (131)I whole body scan, treatment with high doses of (131)I may have therapeutic utility in patients with lung metastases and, to a lesser extent, in those with lymph node metastases. However, in view of the frequent normalization of Tg values in untreated patients, we believe that treatment with (131)I should be considered according to the result of the first posttherapy scan. If positive in the lung, (131)I treatment should be continued up to total remission; surgical treatment should be preferred in patients with node metastases, and no treatment should be used in those with thyroid bed uptake or no uptake.

131I therapy for differentiated thyroid cancer leads to an earlier onset of menopause: results of a retrospective study

Treatment with 131I for differentiated thyroid cancer may give a follicle-damaging radiation dose to the ovaries. This damage to the ovarian function could shorten the fertile life span and advance the natural menopause. To address this issue, we studied retrospectively the menopausal age of 130 women treated with 131I for differentiated thyroid cancer in our institution from 1974-1993. The menopausal age of women treated with 131I for differentiated thyroid cancer after total thyroidectomy and subjected to suppressive L-T4 therapy was compared with the menopausal age of a control group including 127 goitrous women who were treated with suppressive L-T4 for a comparable period of time. The cumulative therapeutic 131I dose to cancer patients ranged from 1,110-40,700 MBq (mean +/- SD, 5,308 +/- 5,483 MBq; median, 3700 MBq). All patients chosen for the study were younger than 45 yr when first treated (i.e. first administration of 131I and L-T4 for cancer patients, and institution of L-T4 therapy for goitrous patients), and older than 45 yr at the end of the study period. The menopausal status of both groups was assessed from the clinical records and compared using Kaplan-Meier survival analysis. The menopausal age of cancer women treated with 131I and suppressive L-T4 therapy was less than that of goitrous patients treated with suppressive L-T4 therapy (P < 0.001). We could not detect any relationship between menopausal age and the age at the first or last 131I dose or to the cumulative 131I dose received. These data indicate that 131I treatment is probably associated with an earlier ovarian failure in thyroid cancer patients. Conceivably, the ovarian irradiation by 131I might contribute to the process of the follicular atresia, thus inducing earlier menopause.

RET/PTC rearrangements in thyroid nodules: studies in irradiated and not irradiated, malignant and benign thyroid lesions in children and adults

Rearrangements of the RET proto-oncogene may occur in both naturally occurring and radiation-induced papillary thyroid carcinomas. Conflicting results on the frequency and type of RET/PTC rearrangements have been reported in relation to age, radiation exposure, and histological tumor variant. We designed the present study to evaluate in a single laboratory, using the same methodologies, the pattern of RET/PTC activation in thyroid tumors from different groups of patients (exposed or not exposed to radiation, children or adults, with benign or malignant tumors) in relationship to the above mentioned variables. We studied 154 patients with benign nodules (n = 65) or papillary thyroid cancer (n = 89). In the last group, 25 were Belarus children exposed to the post-Chernobyl radioactive fallout, 17 were Italian adults exposed to external radiotherapy for benign diseases, and 47 were Italian subjects (25 children and 22 adults) with no history of radiation exposure. Among patients with benign thyroid nodules, 21 were Belarus subjects (18 children and 3 adults) exposed to the post-Chernobyl radioactive fallout, 8 were Italian adults exposed to external radiation on the head and neck, and 36 were Italian adults with naturally occurring benign nodules. The overall frequency of RET/PTC rearrangements in papillary thyroid cancer was 55%. The highest frequency was found in post-Chernobyl children and was significantly higher (P = 0.02) than that found in Italian children not exposed to radiation, but not significantly higher than that found in adults exposed to external radiation. No difference of RET/PTC rearrangements was found between samples from irradiated (external x-ray) or not irradiated adult patients, as well as between children and adults with naturally occurring, not irradiated, thyroid cancer. When analyzing the type of RET/PTC rearrangement (RET/PTC1 or RET/PTC3), no major difference was apparent. In addition, eight cases with an unknown RET/PTC rearrangement and three cases with the concomitant expression of RET/PTC1 and RET/PTC3 were found. No significant correlation was observed between the frequency and/or the type of RET/PTC rearrangement and clinical-epidemiological features of the patients such as age at diagnosis, age at exposure, histological variant, gender and tumor-node-metastasis (TNM) categories. RET/PTC rearrangements were also found in 52.4% of post-Chernobyl benign nodules, in 37.5% of benign nodules exposed to external radiation and in 13.9% of naturally occurring nodules (P = 0.005, between benign post-Chernobyl nodules and naturally occurring nodules). The relative frequency of RET/PTC1 and RET/PTC3 in rearranged benign tumors showed no major difference. In conclusion, our results indicate that the presence of RET/PTC rearrangements in thyroid tumors is not restricted to the malignant phenotype, is not higher in radiation-induced tumors compared with those naturally occurring, is not different after exposure to radioiodine or external radiation, and is not dependent from young age. Other factors, probably influenced by ethnic or genetic background, may act independently from or in cooperation with radiation, to trigger the DNA damage leading to RET proto-oncogene activation.

Post-surgical ablation of thyroid residues with radioiodine in Ukrainian children and adolescents affected by post-Chernobyl differentiated thyroid cancer

Post-surgical ablation of thyroid residues with 131-iodine (131-I) is usually recommended after near-total thyroidectomy in high-risk patients, including children, with differentiated thyroid cancer (DTC). We report here the results of post-surgical radioiodine thyroid ablation in 249 children and adolescents of Ukraine with post-Chernobyl DTC initially treated with near-total thyroidectomy at the Institute of Endocrinology and Metabolism in Kiev, during a 2-year period. The patients' age at the time of the Chernobyl accident (1986), ranged from <1 to 14 yr in 223 subjects (children) and from 15 to 18 yr in 26 subjects (adolescents). Six weeks after surgery a diagnostic 131-I whole body scan revealed the presence of residual thyroid tissue in all cases. All patients received one or more courses of radioiodine therapy, for a total of 468 courses. One hundred and twenty-nine out of 249 patients (51.8%) were successfully ablated. The total number of treatment courses needed in these patients was 219. Most patients required multiple doses of radioiodine, only 63 required a single dose. One hundred and twenty patients (48.2%) treated with radioiodine were not ablated and are still under treatment program. The clinical features and the amount of thyroid residue were not different in ablated or not-ablated patients. Our results indicate that in this particular population of post-Chernobyl thyroid carcinomas, thyroid ablation is a rather difficult task. Only 51.8% were successfully ablated. Possible explanation for this finding may be the young age of the patients, other particular features of post-Chernobyl thyroid carcinoma or technical aspects, such as less radical surgical procedures.